1. Field of the Invention
The present invention provides a power transformation device of a powered device in a power over Ethernet system, and more particularly, a power transformation device applicable to 10 Mbs, 100 Mbs, and 1000 Mbs powered devices in a power over Ethernet system
2. Description of the Prior Art
Power over Ethernet (POE) means a technique for providing DC power for terminal equipments (ex. IP phone, wireless network access point, web-camera, etc.) during data transmission in a present Ethernet. A POE system is also named as a power over LAN (POL) system or an active Ethernet system, and is compatible with the present Ethernet system. The IEEE 802.3af standard is a new protocol of the POE system, and is extended from the IEEE 802.3 standard.
According to the IEEE 802.3af standard, a POE system comprises a power sourcing equipment (PSE) and a powered device (PD). The PSE, the management equipment of the POE system, provides power for the PD. The PD, which is a web-phone, web-camera, network access point, PDA, or other Ethernet devices, obtains power from an RJ-45 socket.
Powering the PD over the PSE system can be classified into two ways. One is powering the PD through the fourth and fifth pins and through the seven and eighth pins of an RJ-45 terminal as shown in FIG. 1, and the other is through the first and second pins and through the third and sixth pins of an RJ-45 terminal as shown in FIG. 2. Note that, Arabic numerals (1, 2 . . . 8) shown in FIG. 1 and FIG. 2 represent pin numbers of a catalog-5 (Cat. 5) cable. When the PSE powers the PD through the fourth and fifth pins and through the seventh and eighth pins, the fourth and fifth pins are coupled to a positive electrode, and the seventh and eighth pins are coupled to a negative electrode. When the PSE powers the PD through the first and second pins and through the third and sixth pins, the first and second pins and the third and sixth pins are coupled to electrodes with opposite poles.
In addition, structures of the POE system can be also classified into two types. One is an end-span structure, and the other is a mid-span structure. Under the end-span structure, the PSE provides power for the PD by the way of FIG. 1 or FIG. 2. Under the mid-span structure as shown in FIG. 3, the PSE provides power for the PD through a midspan PSE by the way of FIG. 1.
According to the IEEE 802.3af standard, the PSE can provide power by either the way of FIG. 1 or the way of FIG. 2, while the PD must be applicable to both ways. Such requirement is easily achieved for designs of 10 Mbs and 100 Mbs PDs, because both of the 10 Mbs and the 100 Mbs PDs apply two twisted pairs of a Cat. 5 cable (the first and second pins and the third and sixth pins) for exchanging data, while the other two twisted pairs (the fourth and fifth pins and the seventh and eighth pin) are unused. Therefore, the 10 Mbs and the 100 Mbs PDs applicable to FIG. 1 or FIG. 2 can be easily achieved. However, a 1000 Mbs Ethernet equipment, unlike the 10 Mbs and the 100 Mbs PDs, applies all twist-pairs of a Cat. 5 cable for exchanging data, so that the prior art POE system shown in FIG. 1 to FIG. 3 is not suitable for 10 Mbs, 100 Mbs, and 1000 Mbs PDs.